Wolfram Alpha, a Revolution for the Web?

Why and when would you want to switch from Google, Yahoo or Live?
The answer is quite simple: Wolfram will give you an answer while other search engines will gives you a (too huge) set of related pages where you can go if the title / description seems to fit your query.
Google and other search engine maps the keywords of our query to a set of pages known to be related to this keywords. Whereas Wolfram Alpha will try to compute the answer based on the contents of those pages and extract the exact answer to your query and a bunch of information answering to your query.